AVS 45th International Symposium
    The Science of Micro-Electro-Mechanical Systems Topical Conference Tuesday Sessions
       Session MM+NS+SS-TuM

Paper MM+NS+SS-TuM7
Vacuum Deposited Fluorinated Alkyl Siloxane Films for Adhesion Control in MEMS Devices

Tuesday, November 3, 1998, 10:20 am, Room 324/325

Session: Micro-Science and Tribology of MEMS
Presenter: T.M. Mayer, Sandia National Laboratories
Authors: T.M. Mayer, Sandia National Laboratories
M.P. de Boer, Sandia National Laboratories
N.D. Shinn, Sandia National Laboratories
P.J. Clews, Sandia National Laboratories
T.A. Michalske, Sandia National Laboratories
Correspondent: Click to Email
Monolayer films of polymerized alkyl siloxanes have been employed for surface passivation and adhesion control in MEMS devices. However, reproducible film formation and properties have been difficult to achieve due to process sensitivity to substrate preparation conditions, presence of small quantities of adsorbed water, and the high aspect ratio structures typical of MEMS devices. In contrast to the normal solution coating process using alkyl trichlorosilane precursors, we have developed a vacuum-based film deposition process, using volatile fluorinated alkyl trichloro silane precursors. Reproducible substrate conditions are obtained by UV-ozone oxidation followed by sequential or simultaneous exposure to the chlorosilane precursor and water vapor. Efficient transport of reactants into high aspect ratio structures is accomplished by maintaining Knudsen flow conditions at low pressures. We measure kinetics of film growth by in-situ ellipsometric and quartz-crystal microbalance techniques, and evaluate film composition and structure by XPS and IR spectroscopies. We also measure the work of adhesion and surface energy of coated cantilever beams under equilibrium fracture mechanics conditions. We compare results to uncoated structures, and to structures coated from solution with alkyl and fluoro-alkyl siloxane films. Sandia is a multiprogram laboratory operated by Sandia Corp., a Lockheed Martin Company, for the U. S. Dept. of Energy under contract DE-AC04-94AL85000.